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Context-Dependent Functional Divergence of the Notch Ligands DLL1 and DLL4 In Vivo.

Preuße K, Tveriakhina L, Schuster-Gossler K, Gaspar C, Rosa AI, Henrique D, Gossler A, Stauber M - PLoS Genet. (2015)

Bottom Line: In the anterior PSM, every cell expresses both Notch receptors and ligands, and DLL1 is the only activator of Notch while DLL4 is not endogenously expressed.Testing several aspects of the complex Notch signalling system in vitro, we found that both ligands have a similar trans-activation potential but that only DLL4 is an efficient cis-inhibitor of Notch signalling, causing a reduced net activation of Notch.These differential cis-inhibitory properties are likely to contribute to the functional divergence of DLL1 and DLL4.

View Article: PubMed Central - PubMed

Affiliation: Institut für Molekularbiologie OE5250, Medizinische Hochschule Hannover, Hannover, Germany.

ABSTRACT
Notch signalling is a fundamental pathway that shapes the developing embryo and sustains adult tissues by direct communication between ligand and receptor molecules on adjacent cells. Among the ligands are two Delta paralogues, DLL1 and DLL4, that are conserved in mammals and share a similar structure and sequence. They activate the Notch receptor partly in overlapping expression domains where they fulfil redundant functions in some processes (e.g. maintenance of the crypt cell progenitor pool). In other processes, however, they appear to act differently (e.g. maintenance of foetal arterial identity) raising the questions of how similar DLL1 and DLL4 really are and which mechanism causes the apparent context-dependent divergence. By analysing mice that conditionally overexpress DLL1 or DLL4 from the same genomic locus (Hprt) and mice that express DLL4 instead of DLL1 from the endogenous Dll1 locus (Dll1Dll4ki), we found functional differences that are tissue-specific: while DLL1 and DLL4 act redundantly during the maintenance of retinal progenitors, their function varies in the presomitic mesoderm (PSM) where somites form in a Notch-dependent process. In the anterior PSM, every cell expresses both Notch receptors and ligands, and DLL1 is the only activator of Notch while DLL4 is not endogenously expressed. Transgenic DLL4 cannot replace DLL1 during somitogenesis and in heterozygous Dll1Dll4ki/+ mice, the Dll1Dll4ki allele causes a dominant segmentation phenotype. Testing several aspects of the complex Notch signalling system in vitro, we found that both ligands have a similar trans-activation potential but that only DLL4 is an efficient cis-inhibitor of Notch signalling, causing a reduced net activation of Notch. These differential cis-inhibitory properties are likely to contribute to the functional divergence of DLL1 and DLL4.

No MeSH data available.


Related in: MedlinePlus

Homozygous Dll1Dll4ki mice fail to generate proper somites and form reduced skeletal muscle tissue.Examination of Dll1-dependent (A,B) somitogenesis and (C-F) myogenesis in (a) wildtype, (b) Dll1lacZ/lacZ, (c) Dll1Dll1ki/Dll1ki, (d) Dll1Dll4ki/+ and (e) Dll1Dll4ki/Dll4ki embryos or foetuses. (A)Uncx4.1 in situ hybridisation of E9.5 embryos. (B) Skeletal preparations of E18.5 foetuses (Dll1lacZ/lacZ foetuses do not survive until E18.5; red arrowheads indicate fused ribs or hemivertebrae in heterozygous Dll1Dll4ki skeletons in d). (C)Myogenin in situ hybridisation to visualise differentiating skeletal muscle cells in myotomes of 17–18 somite stage embryos. (D, E,F) Anti-myosin heavy chain (MHC)-antibody staining of sectioned E15.5 foetuses showing intercostal muscles (D), the diaphragm (E), and muscles in the cross-section of forelimbs (F); black arrowheads indicate examples of muscle tissue, red arrowheads show lack of muscle tissue; asterisks label ribs (D) or bones of the forelimb (F).
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pgen.1005328.g003: Homozygous Dll1Dll4ki mice fail to generate proper somites and form reduced skeletal muscle tissue.Examination of Dll1-dependent (A,B) somitogenesis and (C-F) myogenesis in (a) wildtype, (b) Dll1lacZ/lacZ, (c) Dll1Dll1ki/Dll1ki, (d) Dll1Dll4ki/+ and (e) Dll1Dll4ki/Dll4ki embryos or foetuses. (A)Uncx4.1 in situ hybridisation of E9.5 embryos. (B) Skeletal preparations of E18.5 foetuses (Dll1lacZ/lacZ foetuses do not survive until E18.5; red arrowheads indicate fused ribs or hemivertebrae in heterozygous Dll1Dll4ki skeletons in d). (C)Myogenin in situ hybridisation to visualise differentiating skeletal muscle cells in myotomes of 17–18 somite stage embryos. (D, E,F) Anti-myosin heavy chain (MHC)-antibody staining of sectioned E15.5 foetuses showing intercostal muscles (D), the diaphragm (E), and muscles in the cross-section of forelimbs (F); black arrowheads indicate examples of muscle tissue, red arrowheads show lack of muscle tissue; asterisks label ribs (D) or bones of the forelimb (F).

Mentions: Cranial-caudal somite patterning critically depends on DLL1-mediated Notch signalling [38,46,52]. We analysed if DLL4 can functionally replace DLL1 in this process in homozygous Dll1Dll4ki embryos. Unlike embryos that contained at least one wildtype or Dll1Dll1ki allele, homozygous Dll1Dll4ki embryos displayed severely reduced and irregular Uncx4.1 expression (Fig 3A), which indicates disrupted somite patterning and reduced Notch activity in the PSM due to the inability of DLL4 to replace DLL1. Consistent with defective somite formation and the shortened body axis observed in E15.5 foetuses, Dll1Dll4ki/Dll4ki axial skeletons were severely disorganised (Fig 3B). Therefore, expression of DLL4 from the Dll1 locus does not cause a significant rescue of the Dll1 somitogenesis phenotype.


Context-Dependent Functional Divergence of the Notch Ligands DLL1 and DLL4 In Vivo.

Preuße K, Tveriakhina L, Schuster-Gossler K, Gaspar C, Rosa AI, Henrique D, Gossler A, Stauber M - PLoS Genet. (2015)

Homozygous Dll1Dll4ki mice fail to generate proper somites and form reduced skeletal muscle tissue.Examination of Dll1-dependent (A,B) somitogenesis and (C-F) myogenesis in (a) wildtype, (b) Dll1lacZ/lacZ, (c) Dll1Dll1ki/Dll1ki, (d) Dll1Dll4ki/+ and (e) Dll1Dll4ki/Dll4ki embryos or foetuses. (A)Uncx4.1 in situ hybridisation of E9.5 embryos. (B) Skeletal preparations of E18.5 foetuses (Dll1lacZ/lacZ foetuses do not survive until E18.5; red arrowheads indicate fused ribs or hemivertebrae in heterozygous Dll1Dll4ki skeletons in d). (C)Myogenin in situ hybridisation to visualise differentiating skeletal muscle cells in myotomes of 17–18 somite stage embryos. (D, E,F) Anti-myosin heavy chain (MHC)-antibody staining of sectioned E15.5 foetuses showing intercostal muscles (D), the diaphragm (E), and muscles in the cross-section of forelimbs (F); black arrowheads indicate examples of muscle tissue, red arrowheads show lack of muscle tissue; asterisks label ribs (D) or bones of the forelimb (F).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4482573&req=5

pgen.1005328.g003: Homozygous Dll1Dll4ki mice fail to generate proper somites and form reduced skeletal muscle tissue.Examination of Dll1-dependent (A,B) somitogenesis and (C-F) myogenesis in (a) wildtype, (b) Dll1lacZ/lacZ, (c) Dll1Dll1ki/Dll1ki, (d) Dll1Dll4ki/+ and (e) Dll1Dll4ki/Dll4ki embryos or foetuses. (A)Uncx4.1 in situ hybridisation of E9.5 embryos. (B) Skeletal preparations of E18.5 foetuses (Dll1lacZ/lacZ foetuses do not survive until E18.5; red arrowheads indicate fused ribs or hemivertebrae in heterozygous Dll1Dll4ki skeletons in d). (C)Myogenin in situ hybridisation to visualise differentiating skeletal muscle cells in myotomes of 17–18 somite stage embryos. (D, E,F) Anti-myosin heavy chain (MHC)-antibody staining of sectioned E15.5 foetuses showing intercostal muscles (D), the diaphragm (E), and muscles in the cross-section of forelimbs (F); black arrowheads indicate examples of muscle tissue, red arrowheads show lack of muscle tissue; asterisks label ribs (D) or bones of the forelimb (F).
Mentions: Cranial-caudal somite patterning critically depends on DLL1-mediated Notch signalling [38,46,52]. We analysed if DLL4 can functionally replace DLL1 in this process in homozygous Dll1Dll4ki embryos. Unlike embryos that contained at least one wildtype or Dll1Dll1ki allele, homozygous Dll1Dll4ki embryos displayed severely reduced and irregular Uncx4.1 expression (Fig 3A), which indicates disrupted somite patterning and reduced Notch activity in the PSM due to the inability of DLL4 to replace DLL1. Consistent with defective somite formation and the shortened body axis observed in E15.5 foetuses, Dll1Dll4ki/Dll4ki axial skeletons were severely disorganised (Fig 3B). Therefore, expression of DLL4 from the Dll1 locus does not cause a significant rescue of the Dll1 somitogenesis phenotype.

Bottom Line: In the anterior PSM, every cell expresses both Notch receptors and ligands, and DLL1 is the only activator of Notch while DLL4 is not endogenously expressed.Testing several aspects of the complex Notch signalling system in vitro, we found that both ligands have a similar trans-activation potential but that only DLL4 is an efficient cis-inhibitor of Notch signalling, causing a reduced net activation of Notch.These differential cis-inhibitory properties are likely to contribute to the functional divergence of DLL1 and DLL4.

View Article: PubMed Central - PubMed

Affiliation: Institut für Molekularbiologie OE5250, Medizinische Hochschule Hannover, Hannover, Germany.

ABSTRACT
Notch signalling is a fundamental pathway that shapes the developing embryo and sustains adult tissues by direct communication between ligand and receptor molecules on adjacent cells. Among the ligands are two Delta paralogues, DLL1 and DLL4, that are conserved in mammals and share a similar structure and sequence. They activate the Notch receptor partly in overlapping expression domains where they fulfil redundant functions in some processes (e.g. maintenance of the crypt cell progenitor pool). In other processes, however, they appear to act differently (e.g. maintenance of foetal arterial identity) raising the questions of how similar DLL1 and DLL4 really are and which mechanism causes the apparent context-dependent divergence. By analysing mice that conditionally overexpress DLL1 or DLL4 from the same genomic locus (Hprt) and mice that express DLL4 instead of DLL1 from the endogenous Dll1 locus (Dll1Dll4ki), we found functional differences that are tissue-specific: while DLL1 and DLL4 act redundantly during the maintenance of retinal progenitors, their function varies in the presomitic mesoderm (PSM) where somites form in a Notch-dependent process. In the anterior PSM, every cell expresses both Notch receptors and ligands, and DLL1 is the only activator of Notch while DLL4 is not endogenously expressed. Transgenic DLL4 cannot replace DLL1 during somitogenesis and in heterozygous Dll1Dll4ki/+ mice, the Dll1Dll4ki allele causes a dominant segmentation phenotype. Testing several aspects of the complex Notch signalling system in vitro, we found that both ligands have a similar trans-activation potential but that only DLL4 is an efficient cis-inhibitor of Notch signalling, causing a reduced net activation of Notch. These differential cis-inhibitory properties are likely to contribute to the functional divergence of DLL1 and DLL4.

No MeSH data available.


Related in: MedlinePlus